That precedent frames the challenge facing Trump, now the inevitable GOP nominee. Following long-term trends, it’s likely that minorities will cast 30 percent of the 2016 vote, and white women will comprise slightly more of the remainder than white men—just as in 2012. In his absolute best-case scenario, Trump might match the two-thirds of white men that Reagan won in 1984, the party’s modern apex. But given Trump’s astronomical unfavorable ratings among African Americans and Hispanics, it’s not unreasonable to project that Clinton could hold the roughly 80 percent of minority voters who have typically backed Democratic nominees since 1976.
If both those projections held true, and the electorate’s composition followed the long-term patterns, Trump would then need to attract 58 percent of white women to reach a national majority—slightly more than the 56 percent that Romney won. Looking at the equation from the other direction, if Clinton matched the usual Democratic performance with non-white voters and also carried even half of white women, Trump would then need to win more than three-fourths of white men for a national majority, a daunting prospect.
These calculations lead to the same place: Trump almost certainly can’t beat Clinton, or even stay competitive, without constructing a solid advantage among white women. But today he’s trailing Clinton among them in most surveys.